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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Jan Mon 18, 2016 12:27 am 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
So with the new anode soldered in, I popped the chassis back inside, put all the tubes and connections back, and put it on the bulb tester. When I flipped the switch, the 200W light bulb gradually ramped up brightness and then dimmed out within seconds.

Unfortunately, that's the extent of the good news for today. No picture and no sound at all even with the set connected to directly to the wall. The channel indicator light comes on so I know the cord and power switch is working and the set is powered. :(

Update:
After unplugging the set, there was no noticeable discharge when grounding the anode. The troubleshooting guide in the PhotoFact suggests checking the circuit breaker and 2 power rectifiers for a no raster, no sound condition. It also mentions that the tubes are in a series network which would render the set inoperative if any of the tubes are open.

The rectifiers test within 0.5xx V in circuit. Before I take them out of circuit to test, would should be the reference value? Would a continuity test be sufficient as a test for the tubes?

The electrolytic input filter cap holds a charge, but I don't have a meter capable of testing its capacitance at the moment. Since the cap charged, the circuit breaker can be eliminated. Does anyone have a recommendation for a good, inexpensive multimeter for an amateur? There are enough choices and shootout reviews to make a head spin.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Jan Tue 19, 2016 3:21 pm 
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Joined: Apr Sat 06, 2013 2:18 pm
Posts: 365
Location: New Hampshire
For a meter look into a rebuilt Fluke. It will last a lifetime & is very rugged
& accurate. I think some have an ESR built in. Be careful where you buy it.

Rectifiers will check apx .5 to .7 one way & wide open the other on the
"diode" test position. On series string tubes if one filament goes out all will not light
so if the tubes are lighting thats not it. One exception is the HV rect tube.
it runs off the HV & almost never glows.
Check the major B+ supplies next ( bottom left on Sams ). May be one is out.
If not you may have 2 problems.
DO NOT go nuts changing things until you get it working somewhat. That almost
always goes BAD........

GL & 73 Zeno 8)

NelsonM wrote:
So with the new anode soldered in, I popped the chassis back inside, put all the tubes and connections back, and put it on the bulb tester. When I flipped the switch, the 200W light bulb gradually ramped up brightness and then dimmed out within seconds.

Unfortunately, that's the extent of the good news for today. No picture and no sound at all even with the set connected to directly to the wall. The channel indicator light comes on so I know the cord and power switch is working and the set is powered. :(

Update:
After unplugging the set, there was no noticeable discharge when grounding the anode. The troubleshooting guide in the PhotoFact suggests checking the circuit breaker and 2 power rectifiers for a no raster, no sound condition. It also mentions that the tubes are in a series network which would render the set inoperative if any of the tubes are open.

The rectifiers test within 0.5xx V in circuit. Before I take them out of circuit to test, would should be the reference value? Would a continuity test be sufficient as a test for the tubes?

The electrolytic input filter cap holds a charge, but I don't have a meter capable of testing its capacitance at the moment. Since the cap charged, the circuit breaker can be eliminated. Does anyone have a recommendation for a good, inexpensive multimeter for an amateur? There are enough choices and shootout reviews to make a head spin.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Feb Mon 08, 2016 6:19 am 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Hi again,

Thanks zeno for the advice. When I last posted, none of the tubes lit up. While waiting for my new multimeter, I found that the ground pin in the connector to the remote chassis was dislodged. All tubes are now glowing after seating the pin. I've never before been so excited by the sweet sounds of static that now fill the room when I power on the set.

Sadly, the raster situation is unchanged. I put the meter on the two B+ posts on the sweep PCB and the 250V source tested within 1V, but the I'm only getting ~214V at the 530V boost source. I'm not getting the typical discharge from the anode. The voltages in the proximity of the horizontal output tube match the reference values on the schematic for the most part, but I will have to spend some more time for a thorough check. Does this signal horizontal output transformer failure? The horiz. output tube lights, but could the tube be faulty in this scenario?


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Feb Tue 09, 2016 4:10 am 
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Joined: Mar Sun 01, 2009 10:27 pm
Posts: 4541
Location: Ann Arbor, MI
NelsonM wrote:
The voltages in the proximity of the horizontal output tube match the reference values on the schematic for the most part, but I will have to spend some more time for a thorough check. Does this signal horizontal output transformer failure? The horiz. output tube lights, but could the tube be faulty in this scenario?

The low boost voltage means that the horizontal output circuit is not working but does not point to any specific part. One important voltage to measure is the grid of the horizontal output tube. There should be a negative voltage there that should match what the schematic shows. If it is not there than most likely the horizontal oscillator is not running. Also measure the cathode and screen grid of the horizontal output tube. If the cathode is not directly connected to ground (see the schematic) then a high cathode voltage would indicate that too much current is flowing in the output tube.

With the power off you can use an ohmmeter to measure the resistance of the windings of the horizontal output transformer. The measurements will most likely not match the schematic exactly. But large differences would indicate a problem.

_________________
Tom


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Jul Wed 26, 2017 6:26 am 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Ok guys, I'm finally back from my bathroom break :lol:

Dusted her off and measured her B+. Left is reference values, right is measured:

250V = 277V
245V = 268V
235V = 256V
140V = 160V
120V = 103V
530V Boost = 311V

Horizontal Output Transformer winding resistance:
2.65 Ohms = 2.8 Ohms (terminal A & G)
2.4 Ohms = 2.6 Ohms (terminal G & B)

18 Ohms = 18.6 Ohms (terminals 1 & 3)
10.8 Ohms = 10.9 Ohms (terminals 3 & 4)

17GT5 control grid: -38V = -41V
17GT5 screen grid: 140V = 114V (drops slowly)

I've so far tried replacing 2 resistors, an 8.2K 2W and a 470 Ohm 1/2W, in the path to the screen pins and tried switching the 17GT5 with a different one.

Any ideas about how to proceed from here?


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Jul Wed 26, 2017 1:01 pm 
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Joined: Apr Sat 06, 2013 2:18 pm
Posts: 365
Location: New Hampshire
First dont run out & buy a tube tester. They are pathological liars just
like pols.
Hoz osc is running or you wouldnt get the negative grid. Assuming the new
HO tube is OK try the damper next.
You can also try this. Unplug the HV rect plate cap & keep it away from
any metal. Take a well insulated screwdriver & get the tip near the cap from
the flyback (FBT) . You should get a nice 1/2 to 3/4 inch arc. If so its either
the HV rect tube or the work you did on the socket.

Zeno 8)
LFOD !


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Wed 02, 2017 7:57 pm 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Huzzah! A new damper and rectifier tube brought the CRT back to life. B+ is now ~515V Unfortunately, I think that is where my luck and this story ends.

While the contrast is pretty strong, the raster is rather dim and the outer rim of the screen is somewhat blurry and out of focus. Does this spell of a weak CRT tube? The brightness pot starts to show a picture half way through its full rotation.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Thu 03, 2017 1:25 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 155
Location: parkersburg west virginia
NelsonM wrote:
Huzzah! A new damper and rectifier tube brought the CRT back to life. B+ is now ~515V Unfortunately, I think that is where my luck and this story ends.

While the contrast is pretty strong, the raster is rather dim and the outer rim of the screen is somewhat blurry and out of focus. Does this spell of a weak CRT tube? The brightness pot starts to show a picture half way through its full rotation.


Now that it is playing, does it show a full picture? the best thing to do is let it play for a while & see if the picture gets brighter. it may be that the set has sat unused for a long time & the crt may need time to warm up.
if the picture is squeezed in, you still may have some issues in the horizontal sweep circuit or power supply.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Thu 03, 2017 3:36 pm 
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Joined: Apr Sat 06, 2013 2:18 pm
Posts: 365
Location: New Hampshire
See if its "blooming" . If as you turn up the brite the pix expands & gets darker
thats blooming. If it is 95% HV rect tube.

Most CRT's slowly get poor emission when weak. Symptoms are dark, poor focus,
negative pix, glassy pix, streaking from bright scenes in any combination.
As the set warms up it usually gets better. Also if run with brite & contrast
low in a dark room it will be better. Same idea with color CRT's but can effect
1, 2, or all 3 guns. Sometimes a tube will wake up & get much better with frequent
use.

73 Zeno 8)


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Thu 03, 2017 4:17 pm 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Thanks guys.

In the current state, I'm not sure if it's dim because it's just the snow that I'm seeing, it's been sitting as you've suggested, or I've forgotten how bright CRTs used to be compared to modern displays. Analog broadcast has been gone from the metro NY area for a while now so I'd need to get a digital to analog converter and a RF modulator to put a picture on the screen. In the past year, I managed to track down a Selectra ultrasonic remote. It's had a pretty rough life, but it would be interesting to see it working. Probably not the wisest decision not having known the state of the transformer or CRT :mrgreen:

I'll try to post up a video this weekend of the condition.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Sun 13, 2017 11:23 pm 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Well, finally got a picture on it.
https://drive.google.com/open?id=0B-DRpNUuCzbPSHk0elh6WHE5cFU

Here's a quick video:
https://www.youtube.com/watch?v=kIRp4ad_hls

It's terribly out of focus right now. Brightness is kind of low, but acceptable. Audio is now another problem. It's on max in the video. Static is loud, but audio is low and noisy. Brightness adjustment doesn't cause any blooming as far as I can tell. The flickering on the moire testing portions in the video are compression artifacts. It wasn't jumping like that on the actual screen.


Last edited by NelsonM on Aug Mon 14, 2017 2:45 am, edited 2 times in total.

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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 2:14 am 
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Joined: Sep Fri 07, 2007 2:27 am
Posts: 5236
Location: Grand Chute, Wisconsin
NelsonM wrote:

403. That’s an error.

Your client does not have permission to get URL /IZj8L7dgbGXtG-xz-kYwIdzeFydtnC4bRD6MawLdszWDZ5KdKfMxRIbZXYuo3ATMevoKgyXctoNTI_4=w3840-h1852-rw from this server. (Client IP address: 184.59.235.157)

.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 2:45 am 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Grr.. Sorry, it should be fixed now:

https://drive.google.com/open?id=0B-DRpNUuCzbPSHk0elh6WHE5cFU


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 4:33 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 880
Location: Dallas, TX
I'm not sure if this was mentioned but if you are not using an isolation transformer the chassis is electrically hot on this set.
There should be some sort of focus control. Some later sets used a jumper connection the let you select three or so focus voltage options. However since there are other problems it could be that the focus problem is related to low supply voltage or the like.
The picture and sound problems may be due to a weak RF or IF tube.
I noticed from one of your photos that it looks like some of the shafts on the small adjustment knobs do not connect to the controls.

_________________
Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 4:52 am 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
I wasn't sure if I should adjust the settings or correct the underlying problems first. Maybe a new set of tubes and a few caps. It looks like I should just get a new set of tubes for the set since I don't have a tester. They all look fine visibly with silvery get, but the damper proved deceptive. Does anything shown so far point to a bad CRT? This free TV is racking up quite a bill.

I didn't realize it was a hot chassis. I appreciate the warning! One of the knobs were broken, but I've been plugging in a good knob to adjust the pots.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 5:40 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5279
Location: Woodinville, WA USA
Based on the pics you posted, I wouldn't assume your CRT is bad at this time. Be aware that old tube TVs generally won't have the same super-bright image as a modern flat screen.

I would not waste money replacing all of the other tubes. I have restored various old TVs, and in most cases nearly all of the tubes were fine.

There's one helpful, low-cost thing you can do, and that is to clean (with DeOxit or similar) all of the tube pins and sockets, as well as the controls (volume, etc.). This article has more:

https://antiqueradio.org/FirstStepsInRestoration.htm

The article also explains how to do a simple ohmmeter test to check whether a tube is a total dud (burned-out filament). Your TV wouldn't look as good as it does, if it had a bunch of dead tubes. But checking the filaments won't do any harm, and if you do that check while you're cleaning the tube pins/sockets, it doesn't take long.

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 4:40 pm 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Oh wow, Phil himself. I read your very informative articles a while ago. I just assumed that, since all the the tubes were glowing in the "series tube network", that the filaments were good. I'll pull and test the tubes and grab a can of electrical contact cleaner from the auto parts store as you've instructed.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 5:38 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5279
Location: Woodinville, WA USA
If a tube is glowing, you don't need to test its filament. Cleaning is always a good idea, though.

Phil Nelson


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 5:39 pm 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 913
Location: Wyoming, Michigan
Attachment:
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phpzKld8wAM.jpg [ 43.43 KiB | Viewed 2020 times ]


Photo at a glance. It's generally inconsiderate to ask others to look elsewhere or do their own research when asking for help. Imposing even a slight inconvenience will tend to lose your audience. Just a friendly piece of advice.

Several problems. Circle should be round, you have excessive height. Bad focus as stated (unless bad photography). White shadows to the right of every dark object should not exist (failure of video-ringing damping capacitor(s) or tube). Uneven lightness of background from top to bottom at the right and left borders hints at poor HV regulation and possibly PS hum in video. Lack of stripes in vertical target wedges suggest poor video frequency response (anouther bad cap or tube or possibly a severely misadjusted IF transformer). Overall dimness could be weak CRT, could be poor HV, could be drifted parts in brightness-control circuitry. CRT needs to be checked with a CRT tester.

Capacitors fail with time regardless of hours played. Seems like you still have a lot of them to replace. Buying a full set of tubes would be overkill. At least before it's recapped.

Surely there must be a radio club in the NYC area with a monthly meeting with a volunteer with a tube and/or CRT tester. Contact one and ask for help. By 1967 most TVs used multi-section (compactrons) tubes that are TV-specific and have no other demand (hi-fi audio, antique radio) so are very cheap or possibly free. If you post the list of tubes (from the Sams folder parts list) you might be able to get pre-tested replacements for cheap or just postage costs right here, or at said club meet. Capacitors you just gotta seek and destroy on your own, making a list and buying a whole set from Sal or JustRadios or Mouser or DigiKey or Allied (but best not eBay) can be done on a budget. Wholesale replace of caps is not unreasonable. Wholesale replace of tubes is likely an unnecessary expense.

Jumping to conclusion of bad CRT is probably wrong (or certainly premature). Even if it's the problem here, a Beltron cleaning/rejuvination procedure still might give you years of service from it yet. Still much more likely it's something else.


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 Post subject: Re: Sears Silvertone Medalist All Channel
PostPosted: Aug Mon 14, 2017 6:44 pm 
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Joined: Dec Mon 14, 2015 7:54 am
Posts: 25
Location: New York City
Sorry about that. The forum imposes a size restriction and the BB code here doesn't allow width resizing of embedded images which is why I chose to link off-site. Having began with only a basic understanding of soldering and being watch the Dick Van Dyke Show on a 52 year old TV that hasn't projected since the early 80s is just incredible to me and I only have the people on this forum, the content of shango066 and the like on YouTube, and the resources of the community to thank. It certainly wasn't my intention to turn anyone away. I'll post directly here from now on out.

Thanks for the info. I will look into a recap. From what I've found, there are more radio meets and clubs than there are TV ones around here. There's an old electronics service shop around the block from me that's been around since 1953 still advertising TV and radio parts and repairs on a faded hand painted sign in the window. The owner basically shooed me away, informing me they stopped servicing TVs and sold off their stuff nearly 20 years ago. He couldn't even tell me where I could find resistors and capacitors locally. That's the state of the hobby here in NYC, not even the army of bearded vintage gear head hipsters can spark its resurgence. I wish I could post a scan of the SAMS, but I gather that's probably not allowed here. Below is a list of tubes that I'll be cleaning up this week.

22DE4 damper - purchased
1K3GT HV rect - purchased
17GT5 H. out - purchased
8FQ7 H. mult - ?
13GF7 V. mult/V. out - ?
4HS8 Sync sep/AGC keying/Noise canceller - ?
11KV8 Video output - ?
4EH7 1st video IF - ?
4EJ7 2nd video IF - ?
11KV8 Sound IF - ?
17BF11 Audio out - ?
19DWP4 CRT - ?

It's been scary constantly reading and hearing how important it is to determine the health of the CRT before doing any work and the difficulty in finding replacements. After all the assurances, I won't be so quick to give up on this thing. Thanks again to everyone.


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